---
title: "How Can an Assembly Jam When Every Spacer Is Within Drawing Tolerance?"  
description: "How Can an Assembly Jam When Every Spacer Is Within Drawing Tolerance?"  
author: "Paulina Lewandowska"  
published: 2026-10-18  
canonical: https://answers.mindstick.com/qa/117877/how-can-an-assembly-jam-when-every-spacer-is-within-drawing-tolerance  
category: "Mix Category"  
tags: ["manufacturing", "Mechanical Design", "Dimensional Tolerances", "quality control"]  
reading_time: 1 minute  

---

# How Can an Assembly Jam When Every Spacer Is Within Drawing Tolerance?

We assemble four spacers end to end inside a machined pocket. Quality inspection has accepted the individual parts, but some combinations fit freely while others need force.

## The dimensions we are working with

- Each spacer: **10.00 mm ± 0.10 mm** along the stacking direction.
- Pocket length: **40.20 mm ± 0.10 mm**.
- Assembly requirement: at least **0.05 mm total end clearance**, with no press fit intended.

The nominal dimensions leave clearance, so I suspect our drawing review missed the tolerance stack-up. We need interchangeable parts rather than an operator selecting spacers until a set fits.

Should this be assessed using worst-case tolerance analysis, or could a statistical tolerance stack-up be justified for production? What measurement data and assumptions would be needed before trusting the statistical approach?

I would like to understand how to set tolerances around the assembly requirement without unnecessarily tightening every component dimension.


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Original Source: https://answers.mindstick.com/qa/117877/how-can-an-assembly-jam-when-every-spacer-is-within-drawing-tolerance

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